The invention relates to a device, a method and a system for optically determining particle properties, in particular size and reflectivity. The device comprises at least one light source assembly having at least one light source, a polarizer assembly, at least one sample holder—which can be illuminated by the at least one light source assembly—for accommodating particle preparations to be investigated, at least one analyzer assembly, and at least one imaging device with at least one color-resolving matrix image sensor.
The automatic measurement of particles with computer systems which are connected to an enlarging device is known. Particle properties such as shape, diameter and other geometric dimensions are detected by recording an image of the particles which is processed using a threshold detection method. This is normally done using so-called crossed polarized light. This means that the light is first linearly polarized by a polarizer in a polarization direction, and after being reflected by the particles to be investigated, is guided through an analyzer that has a linear polarization filter, the polarization direction, or respectively polarization plane, of which is at a 90° angle to the polarization plane, or respectively polarization direction, of the polarizer. This yields the best separation of particles from a bright background.
Other particle properties such as the reflectivity, or respectively reflection intensity, and hence the type of particles (metal or nonmetal) are detected by taking a second image using parallel polarized light, i.e., under imaging conditions in which the polarizer and analyzer are positioned parallel with respect to their polarization planes. Alternatively, the second image is taken without a polarizer with unpolarized light, and/or without an analyzer while retaining the effect.
The entire classification of the particles according to size and type hence requires two different images which are recorded under two different lighting conditions.
In the known method, the first image is typically recorded while the polarization directions of the polarizer and analyzer are perpendicular to each other, whereas the second image is recorded while the two are positioned parallel. The chronological sequence of the two images is unimportant. The shape and hence geometric dimensions of the particles are obtained from the image which was recorded with the crossed polarizer and analyzer, and the analysis of the second image with a parallel polarizer and analyzer reveals whether or not the particles are reflective by the brightness resulting at the location of the particles in this configuration.
Contrastingly, an object of the present invention is to accelerate and simplify the characterization of particles.